I have some GM 624 casting heads I was going to use on a very mild street 383 build up. They had a valve then job and sat around a long time, so I figured I'd clean them up & use them. The first exhaust valve I pull out and see a huge crack down the valve guide. A pic would tell it all, but I dont have a working camera :mad:

The crack is on the spring side of the head, under the valve seal, along the valve guide (this is an exhaust valve). I'm not sure on how new valve guides are installed, but it looks like the old guide was drilled/pressed out & this new one was pressed in & thats when the crack happened. Its big but was completely hidden under the umbrella valve seal, but its as long as the umbrella valve seal is. There is zero damage on the combustion chamber/runner side of the head, all damage is on the "spring" side. I can see no realistic fix for it, it does look like no parts will break off though (if theres a good side to this!).

Am I looking for trouble if I go ahead & use these heads assuming all the rest of them are Ok? Would this cause oil to leak down between the guide & the head itself (old guide)???

I'm real gun-shy to use these heads because they were on a engine that never ran right-random popping in the exhaust. We never found the cause of that but I hope this isnt it!!
Thanks!

A little more info. This engine is a very mild 383, the lift on the cam is below 450 and wont see anything wild. Just a driver.

I slept on it & cant use these heads, I dont feel good about it. Well, I always wanted to do a Vortec build, lol!

If they installed the .500" guides it's easy to crack what's left of the factory guide if you don't remove the material. If oil could leak into the port the guide would fall out, you shouldn't have any problems with those heads if the guides were installed correctly.

Thanks Rust ;)
I pulled both of them apart & 7 of the 8 exhaust guides are the same way. One of them has 1/2 the "original" material missing. These are the .500" guides too like you said.
I'm finding it hard to believe a shop would let that many go if it could cause a problem. Heck with it, I'm using them!

We see it all the time with heads that were previously rebuilt from other shops. It's not likely that material will ever flake off anyways. Back when we used the cast iron 1/2" guides, we used to trim the stock guides down to the larger inner boss before driving in the guides, but of course you couldn't use the positive seals that came in the gasket sets, they don't fit the smaller OD guide.

Thanks again Rustbucket, I really appreciate it. :bowtie:
With the price of new heads so cheap I hardly ever use rebuilt GM ones anymore, I kinda forget about stuff like this!

I spent all day cleaning them up & getting them ready. Sunday they'll be on the engine ;)

No problemo :bowtie:

i agree with rust,, also, enginetech makes positive valve stem seals that press on the .502 guides for the 11/32" stem valves. if you trim off the excess guide material left on the head,, before installing the new guide,, or before machining the guide bore i.d. out,, as rust mentioned,, the enginetech seals work like normal positive seals pressed on the .502 guides. hope that helps.